FILE - In this March 21, 2018, file photo, Border Patrol agent Lonnie Swartz, left, arrives at U.S. District Court in downtown Tucson, Ariz., where opening arguments began in his murder trial in Tucson. Swartz will face a second trial Tuesday, Oct. 23, 2018, in the killing of a 16-year-old Mexican teen across the international border. Swartz was acquitted of second-degree murder in Tucson earlier in the year and now will be tried on voluntary and involuntary manslaughter charges. (Ron Medvescek/Arizona Daily Star via AP, File)

FILE - In this Friday, Oct. 9, 2015, file photo, supporters from a number of humanitarian groups gather at a vigil for border shooting victim Jose Antonio Elena Rodriguez in front of the federal courthouse in Tucson, Ariz., preceding the arraignment of Border Patrol Agent Lonnie Swartz in the October 2012 shooting. Swartz will face a second trial Tuesday, Oct. 23, 2018, in the killing of a 16-year-old Mexican teen across the international border. Swartz was acquitted of second-degree murder in Tucson earlier in 2018 and now will be tried on voluntary and involuntary manslaughter charges. (Ron Medvescek/Arizona Daily Star via AP, File)

FILE - In this July 29, 2014, file photo, Araceli Rodriguez handles a rosary during a news conference in Nogales, Mexico, that belonged to her son Jose Antonio Elena Rodriguez, pictured behind her, who was shot and killed by a U.S. Border Patrol agent in October 2012. Border Patrol agent Lonnie Swartz will face a second trial Tuesday, Oct. 23, 2018, in the killing of 16-year-old Elena Rodriguez across the international border. Swartz was acquitted of second-degree murder in Tucson earlier in 2018 and now will be tried on voluntary and involuntary manslaughter charges. (Kelly Presnell/Arizona Daily Star via AP, File)

FILE - In this Dec. 4, 2017, file photo, a portrait of 16-year-old Mexican youth Jose Antonio Elena Rodriguez, who was shot and killed in Nogales, Sonora, Mexico, is displayed on the Nogales street where he was killed that runs parallel with the U.S. border. A U.S. Border Patrol agent will face a second trial Tuesday, Oct. 23, 2018, in the killing of Elena Rodriguez across the international border. Lonnie Swartz was acquitted of second-degree murder in Tucson earlier in 2018 and now will be tried on voluntary and involuntary manslaughter charges. (AP Photo/Anita Snow, File)

TUCSON, Ariz. (AP) — Federal prosecutors will once again try a U.S. Border Patrol agent who killed a 16-year-old boy in a cross-border shooting. The agent was acquitted earlier this year of murder, but a jury deadlocked on manslaughter charges.

A jury was selected Tuesday and opening arguments are scheduled Wednesday in the second trial of Lonnie Swartz, five years since he fatally shot Jose Antonio Elena Rodriguez through a border fence dividing Arizona and Mexico.

The U.S. Attorney's Office has declined to comment on why it decided to pursue manslaughter charges again.

It's extremely rare for a Border Patrol agent to be criminally charged in circumstances involving a use of force case, but the agency was under heavy scrutiny over violent incidents when Swartz was first indicted in 2015, including many involving rock-throwers.

In the meantime, a civil rights lawsuit filed by the ACLU on behalf of Elena Rodriguez's mother has been making its way through the courts but will likely have to be taken up by the Supreme Court before a decision is made.

That's because his attorneys have argued that the American constitution didn't extend to Elena Rodriguez, a Mexican teen who was on Mexican soil when Swartz shot him. The 9th U.S. Circuit Court of Appeals, in an opinion conflicting with a different circuit, recently ruled that Swartz can be held accountable.

Swartz has been on leave and living in Nevada since the incident.

Prosecutors this spring focused on what they said was Swartz's frustration with rock-throwers. Assistant U.S. Attorney Wallace Heath Kleindienst said during closing arguments that Swartz "was fed up with being rocked" after being targeted in at least six other attacks.

Defense attorney Sean Chapman said there was "not a scintilla of evidence" that Swartz was angry or fed up. Chapman said Swartz opened fire because he was trying to protect himself and his fellow agents during a drug operation.